<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <form id="submit">
        <p><input type="text" id="user"></p>
        <input type="submit">
    </form>
    <script>
        // 档表单的submit按钮被点击的时候，表单会触发onsubmit事件
    var submit=document.getElementById("submit");
    var user=document.getElementById("user");
    submit.onsubmit=function(event){
        if(user.value=="quan"){
            window.location.href="https://www.baidu.com";
        }
        event.preventDefault();
    }
    </script>
</body>
</html>